A Chemosensing Ensemble for the Detection of Cysteine Based on the Inner Filter Effect Using a Rhodamine B Spirolactam

A fluorescent chemosensing ensemble for the detection of cysteine is designed based on the fluorescence inner filter effect. The method employs the coordination of Cu²⁺ ion with salicylaldehyde rhodamine B hydrazone (I), a colorless and non-fluorescent rhodamine B spirolactam derivative to form I-Cu(II), a pink color but weakly fluorescent complex. When rhodamine B was introduced to the I-Cu(II) complex solution, the fluorescence signal of rhodamine B is dramatically decreased because of the fluorescence inner filter effect (IFE). Upon adding cysteine to the above solution, it can complex preferentially to Cu²⁺ compared to I, and the I-Cu(II) complex dissociates, which thus decreases the fluorescence IFE of the solution, and in turn leading to the fluorescence increase of the chemosensing system. Based on the above mechanism, a fluorescent chemosensing ensemble for cysteine is developed. The fluorescence increase is linearly with cysteine concentration up to 10.0 μ mol L⁻¹, with a detection limit of 1.4 × 10⁻⁷ mol L⁻¹ (3σ). The optimal conditions of the proposed method were studied and the selectivity of the proposed method was investigated in this paper.     

PMR Assay of Natural Products in Pharmaceuticals. IV Assay of Codeine and Simultaneous Detection of Morphine

A rapid, accurate and precise PMR method is presented for the quantitative determination of codeine and codeine phosphate as bulk drugs and in tablet dosage form. The determination is based on the integration of the C-3 methylprotons or the two aromatic protons of codeine or its salt relative to that of the nine protons of t-butanol. Standard deviations of ± 1.39, 0.27 and 0.65% were obtained for codeine, codeine phosphate bulk drug and codeine phosphate tablets respectively. The method furnishes a specific means of identification of codeine as well as of the simultaneous detection and possible determination of morphine; thus fulfilling one of the most important pharmacopeial requirements for the purity of codeine.     

Solid-Phase Spectrophotometric Determination of Beryllium at ng mL−1

Abstract

A microdetermination method at ng mL^?1 level for beryllium by solid-phase spectrophotometry was been developed. Chrome Azurol S was used as chromogenic reagent to form a blue complex which was easily and strongly sorbed and concentrated on a dextran-type anion-exchange resin. The resin-phase absorbances at 594- and 800 nm were measured directly. Beryllium could be determined over the 1.5 - 15.0 ng mL^?1 range with a RSD of 2.7 % by using 100 mL of sample solution. The detection limit was 0.21 ng mL^?1. By using only 10 mL of sample solution, the calibration graph was linear over the concentration range 10–85 ng mL^?1, the RSD being 1.2 %. The method was applied to the determination of beryllium in underground and mining waste water samples and in beryl mineral.     

Sensitive Spectrofluorimetric Determination of Cytochrome c with Spirocyclic Rhodamine B Hydrazide in Micellar Medium

A new spectrofluorimetric method for the determination of cytochrome c using spirocyclic rhodamine B hydrazide (RBH) as fluorogenic reagent in the presence of sodium dodecylbenzene sulfonate (SDBS) surfactant micelles was developed. The method was based on the reaction of cytochrome c with RBH, a colorless, nonfluorescent spirolactam of rhodamine B in SDBS micelles to give highly fluorescent rhodamine B and hence led to a large increase in fluorescence intensity. The dynamic range and detection limit for the determination of cytochrome c are 4.0–120 ng ml⁻¹ and 0.87 ng ml⁻¹ (3σ), respectively. The optimal conditions for the detection of cytochrome c were evaluated and the possible detection mechanism was also discussed.     

Monte Carlo Calculations of XRF Intensities in Annular Arrangements of Radioactive Source,Sample, Cylindrical Collimator and Detector

ABSTRACT

A Monte Carlo (MC) computer program for the calculation of the distribution of characteristic X-ray intensities as a function of the counting geometry is described. The program evaluates the contribution to the intensities of a fluorescent line from each point of the source, sample and detector. The main considerations of the calculation are based on the critical nature of the internal geometry of the main analyzer components within an energy dispersive X-ray fluorescence (EDXRF) spectrometer. The K XRF intensities for the inner and outer radius of the annular-sample and collimator radius were measured. An optimum geometry can be obtained by varying the collimator radius and the detector-sample distance. The results of the calculations show that the intensity distribution of the radioisotope excited fluorescent radiation through annular sample area is strongly dependent on the collimator radius, with a maximum intensity effect with a smaller sample area and with decreasing collimator radius. An investigation of the XRF intensities in the annular sample surface as a function of collimator radius is discussed.     

Development and validation spectroscopic methods for the determination of lomefloxacin in bulk and pharmaceutical formulations

Four simple, sensitive spectrophotometric and spectrofluorimetric methods (A-D) for the determination of antibacterial drug lomefloxacin (LMFX) in pharmaceutical formulations have been developed. Method A is based on formation of ternary complex between Pd(II), eosin and LMFX in the presence of methyl cellulose as surfactant and acetate-HCl buffer pH 4.0. Spectrophotometrically, under the optimum conditions, the ternary complex showed absorption maximum at 530 nm. Methods B and C are based on redox reaction between LMFX and KMnO₄ in acid and alkaline media. In indirect spectrophotometry method B the drug solution is treated with a known excess of KMnO₄ in H₂SO₄ medium and subsequent determination of unreacted oxidant by reacting it with safronine O in the same medium at λ_max = 520 nm. Direct spectrophotometry method C involves treating the alkaline solution of LMFX with KMnO4 and measuring the bluish green product at 604 nm. Method D is based on the chelation of LMFX with Zr(IV) to produce fluorescent chelate. At the optimum reaction conditions, the drug-metal chelate showed excitation maxima at 280 nm and emission maxima at 443 nm. The optimum experimental parameters for the reactions have been studied. The validity of the described procedures was assessed. Statistical analysis of the results has been carried out revealing high accuracy and good precision. The proposed methods were successfully applied for the determination of the selected drug in pharmaceutical preparations with good recoveries.     

A Fluorescence Turn-on Sensor for Hg<Superscript>2+</Superscript> with a Simple Receptor Available in Sulphide-Rich Environments

Detection of Hg²⁺ in complex natural environmental conditions is extremely challenging, and no entirely successful methods currently exist. Here we report an easy-to-prepare fluorescent sensor B3 with 2-aminophenol as Hg²⁺ receptor, which exhibits selective fluorescence enhancement toward Hg²⁺ over other metal ions. Especially, the fluorescence enhancement was unaffected by anions and cations existing in environment and organism. Moreover, B3 can detect Hg²⁺ in sulphide-rich environments without cysteine, S^2- or EDTA altering the fluorescence intensity. Consequently, B3 is capable of distinguishing between safe and toxic levels of Hg²⁺ in more complicated natural water systems with detection limit ≤2 ppb.     

Quantification of Low Concentrations of DNA Using Single Molecule Detection and Velocity Measurement in a Microchannel

We present a novel method for quantifying low concentrations of DNA based on single molecule detection (SMD) for molecular counting and flow measurements inside a microchannel. A custom confocal fluorescence spectroscopic system is implemented to detect fluorescent bursts emitted from stained DNA molecules. Measurements are made one molecule at a time as they flow through a femtoliter-sized laser focal probe. Durations of single molecule fluorescent bursts, which are found to be strongly related to the molecular transit times through the detection region, are statistically analyzed to determine the in situ flow speed and subsequently the sample volume flowing through the focal probe. Therefore, the absolute concentration of a DNA sample can be quantified based on the single molecule fluorescent counts from the DNA molecules and the associated probe volume for a measured time course. To validate this method for quantifying low concentrations of biomolecules, we tested samples of pBR322 DNA ranging from 1 pM to 10 fM (∼3 ng/ml to 30 pg/ml). Besides molecular quantification, we also demonstrate this method to be a precise and non-invasive way for flow profiling within a microchannel.     

Recent Advance of Hydride Generation–Analytical Atomic Spectrometry: Part I—Technique Development

Abstract Hydride generation is the most popular and widely used chemical vapor generation technique and is interesting to analytical chemists as an effective sample introduction method, especially for elemental determination and speciation analysis by analytical atomic spectrometry. The present review provides a literature survey on the hydride generation technique coupled to analytical atomic spectrometry during the past several years, covering the literature on both tetrahydroborate-based hydride generation and non-tetrahydroborate-based hydride generation techniques. Development of other related methods coupled to hydride generation for better analytical performance of analytical atomic spectrometry is included as well.     

Coulomb integrals in Liouville theory and Liouville gravity

The four-point correlation function has been studied in Liouville field theory. If one of the fields is degenerate, such a function is described in terms of Coulomb integrals. Some nontrivial relations for these integrals have been found that can be used to obtain new exact results in conformal field theory. In particular, a four-point correlation function has been calculated in minimal quantum gravity. The result agrees with the results obtained recently by different methods [A. A. Belavin and A. B. Zamolodchikov, JETP Lett. 82, 7 (2005); Theor. Math. Phys. 147, 729 (2006); A. B. Zamolodchikov, Theor. Math. Phys. 142, 183 (2005); I. K. Kostov and V. B. Petkova, Theor. Math. Phys. 146, 108 (2006)]. The text was submitted by the authors in English.     

Isotope-Ratio-Monitoring Liquid Chromatography Mass Spectrometry (IRM-LCMS): First Results from a Moving Wire Interface System

Abstract

A Liquid Chromatography-Combustion (LC-C) Interface, based on a moving wire technique, has been built and tested. The LC effluent is deposited onto a transport wire, which carries the sample through solvent evaporation and combustion ovens. CO₂ from the combustion step is analysed in an isotope ratio mass spectrometer. Performance of the interface was tested by loop injections of sucrose and glucose into a liquid flow of methanol/water (80/20). Accuracy and precision of δ¹³C_PDB < 1‰ was achieved for sample concentrations > 500 ng/ul (5μl loop), sufficient for studies at natural isotope ratios. In case of ¹³C tracer applications the detection limit was determined to be about 20 pg carbon tracer (on wire).     

FTIR Spectrophotometric Methods Used for Antioxidant Activity Assay in Medicinal Plants

Abstract: Fourier transform infrared spectroscopy (FTIR) is a fast and nondestructive analytical method. Associated with chemometrics, it is a powerful tool for research and industry. The present review discusses the antioxidant activities assay of some plants (fruits, leaves, aerian part) with medicinal properties using an FTIR spectrophotometric method in comparison with other ultraviolet-visible (UV-Vis) spectrophotometric methods. A good correlation was found between the different methods used for measuring the antioxidant capacity of some of these herbs.     

A new water treatment technology for degradation of B[a]A by hydrodynamic cavitation and chlorine dioxide oxidation

Managing environmental contamination with Benz[a]anthracene (B[a]A) is essential due to its carcinogenic, teratogenic and mutagenic effects on humans and the environment. At present, the mainly B[a]A degradation methods used are photodegradation, bioremediation and traditional advanced oxidation, although they all have disadvantages. In this study, B[a]A was degraded by hydrodynamic cavitation (HC), chlorine dioxide (ClO₂), or an innovative combination of the two methods. According to high performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC–MS) analysed the degradation products and degradation pathway of B[a]A, with the kinetics of different degradation methods discussed. Under optimal conditions, HC combined with ClO₂ oxidation can further degrade products to achieve ring cleavage. Compared with the two separate degradation process methods, the combined method exerts a synergistic effect on the degradation of B[a]A, with an enhancement factor of 1.48. Experimental results showed that the combination method can realize enhanced complete degradation of B[a]A, reduce ClO₂ requirements, improve efficiency, reduce energy consumption and produce less harmful products with ring cleavage achieved.     

A Simple and Neutral Receptor Acting as a Sensitive and Switch-on Fluorescent Chemosensor for H<Subscript>2</Subscript>PO<Stack><Subscript>4</Subscript><Superscript>−</Superscript></Stack>

A novel artificial anion chemosensor 1 based on 2, 2′-di (4-nitrophenylurea-β-N-yl) -1, 1′-binaphthyl is designed and synthesized for sensing anions including halide ions and oxoanions. The fluorescent emission of the binaphthyl of receptor 1, forming the hydrogen bonding with anions as the sensing mechanism, is monitored in DMSO for detecting anions. In brief, while most of the anion chemosensors are switch-off fluorescent chemosensor, or non-fluorescent sensor, receptor 1 exhibits obviously the switch-on emission during the complexation with H₂PO₄⁻.     

Preparation of Bone Samples in the Gliwice Radiocarbon Laboratory for AMS Radiocarbon Dating

Abstract

In the Gliwice Radiocarbon Laboratory, a system for preparation of samples for AMS dating has been built. At first it was used to produce graphite targets from plant macrofossils and sediments. In this study we extended its capabilities with the preparation of bones. We dealt with 3 methods; the first was the classical Longin method of collagen extraction, the second one included additional treatment of powdered bone in alkali solution, while in the third one carboxyl carbon was separated from amino acids obtained after hydrolysis of protein. The suitability of the methods was tested on 2 bone samples. Most of our samples gave ages >40kyr BP, suggesting good performance of the adapted methods, except for one sample prepared with simple Longin method. For routine preparation of bones we chose the Longin method with additional alkali treatment.     

Development of a Fluorescent Enzyme-Linked DNA Aptamer-Magnetic Bead Sandwich Assay and Portable Fluorometer for Sensitive and Rapid Leishmania Detection in Sandflies

A fluorescent peroxidase-linked DNA aptamer-magnetic bead sandwich assay is described which detects as little as 100 ng of soluble protein extracted from Leishmania major promastigotes with a high molarity chaotropic salt. Lessons learned during development of the assay are described and elucidate the pros and cons of using fluorescent dyes or nanoparticles and quantum dots versus a more consistent peroxidase-linked Amplex Ultra Red (AUR; similar to resazurin) fluorescence version of the assay. While all versions of the assays were highly sensitive, the AUR-based version exhibited lower variability between tests. We hypothesize that the AUR version of this assay is more consistent, especially at low analyte levels, because the fluorescent product of AUR is liberated into bulk solution and readily detectable while fluorophores attached to the reporter aptamer might occasionally be hidden behind magnetic beads near the detection limit. Conversely, fluorophores could be quenched by nearby beads or other proximal fluorophores on the high end of analyte concentration, if packed into a small area after magnetic collection when an enzyme-linked system is not used. A highly portable and rechargeable battery-operated fluorometer with on board computer and color touchscreen is also described which can be used for rapid (<1 h) and sensitive detection of Leishmania promastigote protein extracts (～100 ng per sample) in buffer or sandfly homogenates for mapping of L. major parasite geographic distributions in wild sandfly populations.     

Investigation of the Melt‐Crystallization of Polypropylene by a Temperature Slope Method

Abstract

To investigate the in‐situ ordering process of isotactic polypropylene (iPP) from a melt state, a stationary growth front was prepared by the temperature slope crystallization (TSC) method. During the melt‐crystallization, iPP was crystallized into the α‐phase or β‐phase depending on the crystallizing conditions. The mechanism of the melt‐crystallization at the growth front was precisely observed by wide‐angle and small‐angle x‐ray scattering (WAXS and SAXS) using a strong synchrotron beam. In the TSC apparatus, the sample was crystallized in between a heater, controlled to 220°C, and a cooler, cooled by water to 25°C. We define the z‐axis parallel to the temperature gradient. A‐lamellae and B‐lamellae are also defined as those whose lamellar normal are perpendicular and parallel to the z‐axis, respectively. In a sample‐stop (SS) stage before the TSC, the original α‐phase lamellae became thicker, approaching to the melt‐solid boundary by annealing. The annealing process showed that the α‐phase B‐lamellae remained and the SAXS reflection was stronger on the meridian near the melt‐solid boundary in the SS stage. In the beginning of the TSC, the α‐phase B‐lamellae developed as a primary crystallization. During secondary crystallization under high supercooling, the SAXS cross pattern appeared showing that the α‐phase developed both A‐ and B‐lamellae. As the growth direction of A‐lamellae is parallel to the z‐axis, A‐lamellae grow faster than B‐lamellae. By the self‐epitaxial mechanism on the side surface of the A‐lamellae, the B‐lamellae grow on the base of the A‐lamellae. Following appearance of a spontaneous β‐nucleus, the β‐phase lamellae grew preferentially, excluding the α‐phase, and occupied the whole area of the sample. In this case also, A‐lamellae are advantageous to grow because of the growth direction parallel to the z‐axis. As a result, the SAXS β‐phase reflection appeared on the equator.     

Detection of carcinoembryonic antigen using functional magnetic and fluorescent nanoparticles in magnetic separators

We combined a sandwich immunoassay, anti-CEA/CEA/anti-CEA, with functional magnetic (~80 nm) and fluorescent (~180 nm) nanoparticles in magnetic separators to demonstrate a detection method for carcinoembryonic antigen (CEA). Determination of CEA in serum can be used in clinical diagnosis and monitoring of tumor-related diseases. The CEA concentrations in samples were deduced and determined based on the reference plot using the measured fluorescent intensity of sandwich nanoparticles from the sample. The linear range of CEA detection was from 18 ng/mL to 1.8 pg/mL. The detection limit of CEA was 1.8 pg/mL. In comparison with most other detection methods, this method had advantages of lower detection limit and wider linear range. The recovery was higher than 94%. The CEA concentrations of two serum samples were determined to be 9.0 and 55 ng/mL, which differed by 6.7% (9.6 ng/mL) and 9.1% (50 ng/mL) from the measurements of enzyme-linked immunosorbent assay (ELISA), respectively. The analysis time can be reduced to one third of ELISA. This method has good potential for other biomarker detections and biochemical applications.     

Advances in Electrothermal Atomization Atomic Absorption Spectrometry: Instrumentation,Methods, and Applications

Abstract

Electrothermal atomization (ETA) atomic absorption spectrometry (AAS) offers high sensitivity quantitative analysis of a wide variety of samples for metals. Following an introduction to this instrumental method, recent developments in instrumentation, methods of sample preparation, and significant applications are reviewed, illustrating significant developments. The focus of this review is on the practical application of ETA‐AAS for real sample analysis.     

Application of potassium permanganate to spectrophotometric assay of metoclopramide hydrochloride in pharmaceuticals

Two simple, sensitive, and cost-effective spectrophotometric methods are described for the determination of metoclopramide hydrochloride (MCP) in pharmaceutical dosage forms. The methods are based on a redox reaction between MCP and KMnO₄ in alkaline and acid media. Direct spectrophotometry (method A) involves treating MCP with permanganate in an NaOH medium and measuring a bluish green product at 610 nm. In indirect spectrophotometry (method B), MCP is treated with a fixed concentration of KMnO₄ in an H₂SO₄ medium, and after a specified time, the unreacted KMnO4 is measured at 545 nm. Under optimum assay conditions, Beer’s law is obeyed over the ranges of 0.75–12.0 and 2.5–30.0 g/ml for methods A and B, respectively. Molar absorptivity values are calculated to be 2.33∙10⁴ and 2.66∙10⁴ l/mol cm for methods A and B, respectively, and corresponding Sandell’s sensitivity values are 0.015 and 0.013 g/cm². Limits of detection (LOD) and quantification (LOQ) are also reported. The applicability of the developed methods was demonstrated by the determination of MCP in tablet and injection forms. The accuracy and reliability of the proposed methods were further ascertained by recovery studies via standard addition technique.